Oscillating motor and motor control apparatus and method

ABSTRACT

An oscillating motor includes: a first teeth having a concave portion and a convex portion at its front surface; a stator having the first teeth by pairs formed at an inner circumferential surface; and a rotor having a concave portion and a convex portion at the front surface of a second teeth in a manner of being engaged with the concave portion and the convex portion formed at the first teeth of the stator. The motor can be reciprocally rotated in the rotation region without any conversion device for changing to a linear movement. In addition, it can be simply connected for use to the existing apparatus.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an oscillating motor, and moreparticularly, to an oscillating motor in which a concave portion and aconvex portion are formed at the inner circumferential surface of arotor and a stator to increase contact area, thereby increasing a torqueof the motor, and an AC power applied to the motor is controlled tovariably control the area where the rotor is reciprocally rotated,thereby increasing an efficiency of a compressor.

[0003] 2. Description of the Background Art

[0004] In general, a motor controls an operation of a switching deviceto switch on or off a power supplied to a coil wound on a multi-phasestator, so as to generate a rotational torque. As the excitation stateof the rotor and the stator of the motor is sequentially varied, aforward directional rotational torque is generated thanks to thegenerated magnetic suction force, and if a specific excitation statebetween the rotor and the stator of the motor is not varied, the rotoris stopped at a certain position.

[0005] In addition, by controlling a phase of an input pulse signalapplied to the switching device with formation of the maximum inductanceof the motor as the starting point, a reverse-rotational force isgenerated, and accordingly, the motor can be controlling in its drivingand direction.

[0006] The construction of the motor will now be described withreference to FIG. 1.

[0007]FIG. 1 is a sectional view showing a structure of a motor inaccordance with a conventional art.

[0008] As shown in FIG. 1, the motor includes a cylindrical stator 12, arotor 12 rotatably inserted at the inner side, a rotational shaft 10provided at the center of the rotor 11 as an output shaft, stator teeth14, a coil 15 wound on the stator teeth, a position detecting unit (notshown) for detecting a position of the rotor, and a controller (notshown) for controlling the motor according to a position detected by theposition detecting unit.

[0009] The stator 13 includes six teeth 14 formed protruded at a certainangle (60° at the inner side of the mother body. The coil 15 is wound ateach of the stator teeth 14, making stator poles. The stator poles areelectrically connected to each other in the diagonal direction, to form3 phases (a, b, c) that the same polarity is generated.

[0010] The rotor 11 includes four rotor teeth 12 formed protruded at acertain angle, that is, at a 90°, on the outer circumferential surface.The rotor teeth 12 is rotated with a void formed with an end portion ofthe stator teeth 14.

[0011] As an embodiment of the above-constructed motor, an SRM motorwill now be described.

[0012]FIG. 2 is a circuit diagram showing the construction of the SRMmotor in accordance with the conventional art.

[0013] As shown in FIG. 2, the SRM motor includes a DC link capacitor(C) 26 for smoothing an inputted voltage and supplying the resulted DCvoltage to switched reluctance motor (SRM) motor, coils 27, 28 and 29 ofthe ‘N’ number of motors respectively connected in parallel as many asthe number of ‘N’ phases, upper switch devices 20, 22 and 24 and lowerswitch devices 30, 31 and 32 connected in series vertically to the coils27, 28 and 29 of the motor, free wheel diodes 33, 34 and 35 connectedbetween an emitter of the upper switch devices 20, 22 and 24 and anemitter of the lower switch devices 30, 31 and 32, and freewheel diodes21, 23 and 25 connected between a collector of the upper switch devices20, 22 and 24 and the emitter of the lower switch devices 30, 31 and 32.

[0014] The operation of the SRM motor will now be described in detailwith reference to FIGS. 1, 2 and 3A through 3C.

[0015]FIGS. 3A through 3C show waveforms of periods to control the speedof the motor under the dwell control in accordance with the conventionalart.

[0016] As shown in FIGS. 3A through 3C, the position detecting unitdetects a position of the rotor teeth 12 and outputs a positiondetection pulse to the rotor 13. Then, the rotor 13 synchronizes theposition detection pulse, applies a current to the 3 phases (a, b, c)excitation coil 15 and generates an electromagnetic force.

[0017] That is, when a voltage is inputted to the DC link capacitor 26,the DC link capacitor 26 smoothes the inputted voltage and applies it tothe SRM motor.

[0018] Upon receipt of the smoothed voltage, that is, the DC voltage,the SRM motor is rotated, and by installing a motor interrupter and adisk having a slog related to each phase in the motor, the position ofthe rotor is detected by the photo sensor.

[0019] After the position of the rotor is detected, when the motor isoperated at a low speed, as shown in FIG. 3A, the period of the gatesignal (ga) for controlling the switch device of the motor is madeshortened to control the current applied to the motor.

[0020] In case that the motor is operated at a middle speed, the switchdevice of the motor is controlled with a signal period as shown in FIG.3B, and in case that the motor is operated at a high speed, the switchdevice of the motor is controlled with a signal period as shown in FIG.3C, whereby the current flowing to the motor is controlled to rotate themotor in the forward direction or in the backward direction.

[0021] In the method for controlling the 3 phases of stator coils by thedwell time, the case that the motor is operated at a low speed will nowbe described in detail.

[0022] In order to generate electricity at the phase ‘1’ of the statorcoil and generate an electromagnetic force, a high level of phase ‘a’gate signal (ga) is supplied to a gate of the upper and the lower switchdevices 20 and 33 connected in series to the motor coil 27. When theupper and the lower switch devices 20 and 33 of the phase ‘a’ are turnedon by the high level of gate signal as supplied, a current flows to themotor coil 27 connected in series to the upper and the lower switchdevice, so that electricity is generated at the motor coil 27 of thephase ‘a’.

[0023] After electricity is generated at the motor coil 27 of the phase‘a’ and the current flows to the motor coil 27 of the phase ‘a’ for apredetermined dwell time (T), a low level of gate signal (ga) isoutputted to the upper and the lower switch devices 20 and 30.

[0024] When the low level signal is outputted, the upper and lowerswitch devices 20 and 30 are simultaneously turned on, and the magneticflux generated at the motor coil 27 of the phase ‘a’ is removed whilepassing the DC link capacitor 26 and the motor coil 27, so that thatmotor is smoothly rotated.

[0025] In case that an electromagnetic force is generated at the statorcoil ‘b’, in order generate electricity at the stator coil, the highlevel gate signal (gb) of the phase ‘b’ is supplied to the gate of theupper and lower switch devices 22 and 31 connected in series to themotor coil 28, and accordingly, the upper and lower switch devices 22and 31 of the phase ‘b’ are simultaneously turned on.

[0026] As the upper and lower switch devices 22 and 31 of the phase ‘b’are turned on, the current flows to the motor coil 28, and thus,electricity can be generated at the motor coil 28 of the phase ‘b’.

[0027] When the electricity is generated at the motor coil 28 of thephase ‘b’, the current flows for a predetermined dwell time, and thenthe low level of gate signal (ga) is outputted to the upper and lowerswitch devices 22 and 31.

[0028] When the low level signal is outputted, the upper and lowerswitch devices 22 and 31 are simultaneously turned off, and the magneticflux generated at the coil 28 of the motor of the phase ‘b’ is removedby the free wheel diodes 23 and 34, the DC link capacitor 26 and themotor coil 28, so that the motor can be smoothly rotated.

[0029] In case of the phase ‘c’, it also has the same operations asthose of the phases ‘a’ and ‘b’, thus, descriptions are omitted.

[0030] When current is applied to the stator 13 and the motor isrotated, a microcomputer detects a position of the rotor by means of theposition detecting unit and controls switching of the plurality ofswitch devices 20, 22, 24, 33, 34 and 35, according to which the motoris rotated in the forward direction or the backward direction.

[0031] However, as described above, though the motor can be rotated at ahigh speed in the forward or in the backward direction, it is incapableof making a reciprocal rotational movement at a high speed in a certainarea. Therefore, it fails to be adoptable to a mechanism or a devicewhich needs a high-speed reciprocal movement. In addition, if it ispossibly adoptable, a conversion mechanism for changing a rotationalmovement to a linear movement is to be additionally installed, causing aproblem that its expense is increased.

SUMMARY OF THE INVENTION

[0032] Therefore, an object of the present invention is to provide anoscillating motor in which a concave portion and a convex portion areformed at the inner circumferential surface of a rotor and a stator toincrease contact area, and coils wound on a stator teeth in a diagonaldirection are electrically connected to each other to alternately excitea current flowing to each phase of the coil, thereby making a reciprocalrotational movement even without a current conversion device.

[0033] Another object of the present invention is to provide anoscillating motor in which an AC power applied to the motor iscontrolled to control an operation of the motor in its reciprocalrotation, whereby a rotor of the motor can be operated in a certainrotation range.

[0034] To achieve these and other advantages and in accordance with thepurpose of the present invention, as embodied and broadly describedherein, there is provided an oscillating motor including: a first teethhaving a concave portion and a convex portion at its front surface; astator having the first teeth by pairs formed at an innercircumferential surface; and a rotor having a concave portion and aconvex portion at the front surface of a second teeth in a manner ofbeing engaged with the concave portion and the convex portion formed atthe first teeth of the stator.

[0035] To achieve the above objects, there is also provided a controlapparatus of an oscillating motor including: a motor having a concaveportion and a convex portion formed at a teeth of a stator a concaveportion and a convex portion at a teeth of a rotor; and a controller forcontrolling an AC power applied to the stator to control a reciprocalrotation area and speed of the rotor, so as for the rotor to be rotatedreciprocally in the stator.

[0036] To achieve the above objects, there is further provided a motorcontrol method including: a step in which a switching control signal isoutputted according to a polarity of an AC power when the AC power isinputted; a step in which a switch device is turned on according to theswitching control signal; a step in which a current is applied to thecoil of the stator teeth as the switch device is turned on, so that thecoil electrically connected to the coil of the stator coil and thestator teeth in the diagonal direction are simultaneously excited; astep in which the concave and the convex portions of the rotor areengaged with the concave and the convex portions of the stator in theexcitation direction and rotated to reciprocally rotate in therotational area while the contact surface is being increased; and a stepin which a rotational angle of the rotor is detected and a switchingcontrol signal is variably outputted according to the detecting result.

[0037] The foregoing and other objects, features, aspects and advantagesof the present invention will become more apparent from the followingdetailed description of the present invention when taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings, which are included to provide afurther understanding of the invention and are incorporated in andconstitute a part of this specification, illustrate embodiments of theinvention and together with the description serve to explain theprinciples of the invention.

[0039] In the drawings:

[0040]FIG. 1 is a sectional view showing a structure of a motor inaccordance with a conventional art;

[0041]FIG. 2 is a circuit diagram showing the construction of an SRMmotor in accordance with the conventional art;

[0042]FIGS. 3A through 3C show waveforms indicating period forcontrolling the speed of the motor by a dwell control in accordance withthe conventional art;

[0043]FIG. 4 is a perspective view showing an oscillating motor inaccordance with a preferred embodiment of the present invention;

[0044]FIG. 5 is a vertical-sectional view of the oscillating motor inaccordance with the preferred embodiment of the present invention;

[0045]FIG. 6 is a sectional view taken along line ‘f-f’ of FIG. 5 inaccordance with the preferred embodiment of the present invention;

[0046]FIG. 7 is a sectional view showing a reciprocal rotation area ofthe motor in accordance with the preferred embodiment of the presentinvention;

[0047]FIG. 8 is a circuit diagram showing a driving unit of theoscillating motor in accordance with the preferred embodiment of thepresent invention;

[0048]FIGS. 9A through 9E are wave forms for controlling the drivingunit of the oscillating motor in accordance with the preferredembodiment of the present invention;

[0049]FIG. 10 is a graph showing a comparison of inductance between themotor of the present invention and that of the conventional art;

[0050]FIG. 11 is a graph showing a comparison between a static torque ofthe motor in accordance with the present invention and that of theconventional art; and

[0051]FIG. 12 is a graph showing a comparison between an efficiency ofthe motor in accordance with the present invention and that of theconventional art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0052] Reference will now be made in detail to the preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings.

[0053]FIG. 4 is a perspective view showing an oscillating motor inaccordance with a preferred embodiment of the present invention, FIG. 5is a vertical-sectional view of the oscillating motor in accordance withthe preferred embodiment of the present invention, and FIG. 6 is asectional view taken along line ‘f-f’ of FIG. 5 in accordance with thepreferred embodiment of the present invention.

[0054] As shown in the drawings, there are provided a stator 410, arotor 440 disposed to be rotatable at the inner side of the stator 410,and a rotational shaft 470 making the output shaft at the center of therotor.

[0055] The stator 410 is provided with a stator core 420 that laminationsheets are stacked. A pair of stator teeth with coil wound thereon areformed at reciprocal rotation regions 400 and 400-1 of the front andrear sides except for non-rotation regions 490 and 490-1 at the innercircumferential surface of the stator core 420.

[0056] A coil 430 is wound at a stator teeth 480 to excite the statorteeth 480 by a current applied from an AC power, and a concave portion480 and a convex portion 480 b are alternately formed in the verticaldirection at the front surface of the stator teeth 480.

[0057] The coil 430 wound at the stator teeth 480 are connected to eachother in the diagonal direction, so that when a current is applied tothe coil 430 of the stator teeth 480, the current is also applied to thecoil 430 and the diagonally positioned coil 430. As the coils 430 in thediagonal direction are simultaneously excited to make one phase (La,Lb).

[0058] The rotor 440 is provided with a rotor core 460 that laminationsheets are stacked, and rotor teeth 450 is formed protruded at the frontand rear sides (180° position) of the rotor core 460.

[0059] The rotor teeth 410 and the stator teeth are alternately excitedso that the rotor 440 can make a reciprocal movement in the reciprocalrotation regions 400 and 400-1.

[0060] A concave portion 450 a and a convex portion 450 b arealternately formed in the vertical direction at the front face of therotor teeth 450, so that they are combined with the concave portion 480a and the convex portion 480 b of the stator teeth 20. Thus, the contactarea between the stator 410 and the rotor 440 is increased and a flux isformed wide, and thus, a torque is increased.

[0061] The operation of the rotor teeth and the stator teeth will now bedescribed in detail with reference to FIG. 7.

[0062]FIG. 7 is a sectional view showing a reciprocal rotation area ofthe motor in accordance with the preferred embodiment of the presentinvention.

[0063] As shown in FIG. 7, when a current is applied to the coil 430wound at the stator teeth 480, the electrically connected coil 430 andthe diagonally-directed stator teeth 480 are simultaneously excited, andthe rotor teeth 450 is rotated in a direction that a magnetic resistanceis ‘0’ to generate a rotational torque.

[0064] Since the rotor teeth is rotated in the direction that themagnetic resistance is ‘0’, when a current is alternately applied toeach phase (La, Lb) by means of the switching unit, the rotor 440 isreciprocally rotated in the excitation direction within a predeterminedangle, that is, within the reciprocal rotation regions 400 and 400-1indicated in a dotted line of FIG. 7, and the rotational shaft 470,making the output shaft of the motor, is also reciprocally rotatedwithin a certain angle according to the reciprocal rotation of the rotor440.

[0065] In rotation, the convex portion 450 b of the rotor 440 iscombined to the concave portion 48 a of the rotor 420 and the convexportion 480 b of the rotor 420 is insertedly combined to the concaveportion 450 a of the rotor, so that the flux is formed side inexcitation and the torque is widely generated.

[0066] The apparatus for controlling the reciprocal rotation of themotor in the horizontal direction will now be described in detail withreference to FIGS. 8 and 9.

[0067]FIG. 8 is a circuit diagram showing a driving unit of theoscillating motor in accordance with the preferred embodiment of thepresent invention.

[0068] As shown in FIG. 8, a driving unit of the oscillating motorincludes a first triac 540 being connected in series to a first coil 510of the motor, and applying a current to the first coil 510 to excite aphase ‘a’ when an inputted AC is of a positive polarity; a second triac520 being connected in series to a second coil 530, and being connectedin parallel to the first coil 510 and the first triac 450 to excite aphase ‘b’ when the inputted AC power is a negative polarity; and amicrocomputer (not shown) for controlling the first triac 540 and thesecond triac 520.

[0069] The operation of the driving unit constructed as described abovewill now be explained with reference to FIGS. 9A through 9E.

[0070]FIGS. 9A through 9E are wave forms for controlling the drivingunit of the oscillating motor in accordance with the preferredembodiment of the present invention.

[0071] As shown in FIGS. 9A through 9E, when a current is applied to thecoil 430 wound at the stator teeth 480, the coil 430 electricallyconnected to the coil 430 and the teeth 480 positioned in the diagonaldirection to the electrically connected coil 430 are simultaneouslyexcited, and the rotor teeth 450 of the rotor 440 is rotated in thedirection that the SRM becomes ‘0’ to generate a rotational torque.

[0072] At this time, when the current is alternately applied to thewinding coils 510 and 530 by the first and second switching controlsignal applied to the first and second triacs 520 and 540, the rotor 440repeatedly makes a forward and a backward rotation within apredetermined angle in the excitation direction. Then, according to thereciprocal rotational movement of the rotor 440, the rotational shaft470 of the motor performs a reciprocal rotation within the predeterminedangle.

[0073] That is, when the AC power is of a positive polarity, the firsttriac 540 is turned by the first switching control signal, and thecurrent supplied from the power source passes the first triac 540 to thefirst coil 510, to excite the phase ‘a’.

[0074] When the AC power is a negative polarity, the second triac 520 isturned on by the second switching control signal, and the current whichhas excited the phase ‘a’ and the current of the negative AC power flowto the second coil 530 through the second triac 520, so that the phase‘b’ is excited. These operations are repeatedly performed so that therotor 440 makes the rotational reciprocal movement.

[0075] When the rotor 440 is reciprocally rotated, the microcomputer(not shown) detects a swing angle of the motor and outputs first andsecond switching control signals for varying the magnitude of thevoltage applied to the motor according to the detecting result, tocontrol the first and the second triacs 520 and 540 to be alternatelyoperated.

[0076] A duty ratio of the first and second switching control signalsare varied depending on the magnitude of the voltage applied to themotor.

[0077] That is, in order to control the angle at which the rotor isrotated, after the AC power of a positive polarity is inputted, adriving voltage for turning on the first triac 540 is inputted in apredetermined time (b). Then, since the time during which the positivecurrent flows is constant, the time during which the current flows tothe first coil 510 is shortened and the angle at which the rotor 440 isrotated to excite the phase ‘a’ becomes small.

[0078] A control method for a case that the AC power is a negativepolarity is the same as the case in which the positive current flows,descriptions of which, thus, is omitted.

[0079] The angle at which the motor is reciprocally rotated can becontrolled by controlling time point for applying a driving voltage ofthe first and second triacs when the AC power is applied.

[0080] The effect of the oscillating motor and the control apparatus asstated above will now be described in detail with reference to FIGS. 10,11 and 12.

[0081]FIG. 10 is a graph showing a comparison of inductance between themotor of the present invention and that of the conventional art,

[0082] In the conventional motor, the ratio of the maximum value (Max)and the minimum value (Min) of the inductance is 3, but comparatively,the ratio of the maximum value and the minimum value of the inductanceof the present invention is 4.5. Therefore, the magnetic resistancemotor of the present invention exhibits a 50 increased efficiency whilehaving the same size as that of the conventional motor.

[0083]FIG. 11 is a graph showing a comparison between a static torque ofthe motor in accordance with the present invention and that of theconventional art. Also in the static torque test for measuring a forceof the motor at a current, the magnetic resistance motor of the presentinvention has about 30˜45% increased torque compared to the conventionalmagnetic resistance motor.

[0084]FIG. 12 is a graph showing a comparison between an efficiency ofthe motor in accordance with the present invention and that of theconventional art. According to a measurement result in a dynamo test,the magnetic resistance motor of the present invention exhibits morethan 10% increased efficiency compared to the conventional magneticresistance motor.

[0085] As so far described, according to the oscillating motor of thepresent invention, the coils are wound at the stator teeth of the motorand coils are electrically connected in the diagonal direction toalternately excite the current flowing to each phase in the diagonaldirection, so that the motor can be reciprocally rotated in the rotationregion without any conversion device for changing to a linear movement.In addition, it can be simply connected for use to the existingapparatus.

[0086] Moreover, since the concave portion and the convex portion arecrossly formed at the front surface of the stator and the rotor, so thatthe contact area between the stator and the rotor is increased and thetorque of the motor is also increased.

[0087] Furthermore, since the region where the motor is reciprocallyrotated is controlled by controlling the AC power inputted to the motor,the operational speed of the compressor and the stroke can becontrolled. Thus, the efficiency of the compressor is improved. Also,since no switching device is additionally installed to control theregion where the motor is reciprocally rotated, its expense is reduced.

[0088] As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims, and therefore allchanges and modifications that fall within the meets and bounds of theclaims, or equivalence of such meets and bounds are therefore intendedto be embraced by the appended claims.

What is claimed is:
 1. An oscillating motor comprising: a first teethhaving a concave portion and a convex portion at its front surface; astator having the first teeth by pairs formed at an innercircumferential surface; and a rotor having a concave portion and aconvex portion at the front surface of a second teeth in a manner ofbeing engaged with the concave portion and the convex portion formed atthe first teeth of the stator.
 2. The oscillating motor of claim 1,wherein, at the first teeth, coils are connected in the diagonaldirection to each other, so that when a current is applied to the coils,the diagonally connected coil and the first teeth are simultaneouslyexcited.
 3. The oscillating motor of claim 1, wherein, at the firstteeth, the concave portion and the convex portion are alternately formedto increase a contact area between the rotor and the stator.
 4. Theoscillating motor of claim 1, wherein the second teeth includes theconcave portion and the convex portion at its front face, of which theconcave portion is engaged with the convex portion of the first teeth ofthe rotor and the convex portion is engaged with the concave portion ofthe first teeth of the stator, for rotation, so that the contact areabetween the rotor and the stator is increased, and thus, a magnetic fluxis formed wide.
 5. The oscillating motor of claim 1, wherein the rotoris rotated in a direction that the first teeth is excited, that is, themagnetic resistance is ‘0’.
 6. A control apparatus of an oscillatingmotor comprising: a motor having a concave portion and a convex portionformed at a teeth of a stator and a concave portion and a convex portionat a teeth of a rotor; and a controller for controlling an AC powerapplied to the stator to control a reciprocal rotation area and speed ofthe rotor, so as for the rotor to be rotated reciprocally in the stator.7. The apparatus of claim 6, wherein the controller comprises: a firstswitch unit for applying an applied current to a first excitation unitand exciting a first phase among the stator polarity of 2 phasesgenerated by a coil wound at the stator teeth, when an AC power ofpositive polarity and a first switching control signal are inputted; anda second switch unit for applying an applied current to a secondexcitation unit and exciting a second phase among stator polarity of twophases, when an AC power of negative polarity and a second switchingcontrol signal are inputted.
 8. The apparatus of claim 6, wherein thecontroller includes a microcomputer for detecting a swing angle of areciprocally rotated rotor, varying the magnitude of a voltage appliedto the motor according to the detected value, and outputting the firstand the second switching control signal.
 9. The apparatus of claim 8,wherein the microcomputer varies the magnitude of the voltage applied tothe motor by varying a duty ratio of the switching control signal. 10.The apparatus of claim 7, wherein the switching control signal controlsON/OFF operation of the first and the second switch units, so that thefirst and the second switch units are alternately operated, andaccordingly, the rotor is reciprocally rotated in the reciprocalrotation region.
 11. The apparatus of claim 7, wherein the switchingcontrol signal controls a driving voltage of the first and the secondswitch units to control the amount of current applied to the first andthe second excitation units, thereby controlling the area where therotor is reciprocally rotated.
 12. A motor control method comprising: astep in which a switching control signal is outputted according to apolarity of an AC power when the AC power is inputted; a step in which aswitch device is turned on according to the switching control signal; astep in which a current is applied to the coil of the stator teeth asthe switch device is turned on, so that the coil electrically connectedto the coil of the stator coil and the stator teeth in the diagonaldirection are simultaneously excited; a step in which the concave andthe convex portions of the rotor are engaged with the concave and theconvex portions of the stator in the excitation direction and rotated toreciprocally rotate in the rotational area while the contact surface isbeing increased; and a step in which a rotational angle of the rotor isdetected and a switching control signal is variably outputted accordingto the detecting result.
 13. The method of claim 12, wherein theswitching control signal controls the driving voltage for turning on theswitch, to thereby control the rotation angle of the motor.
 14. Themethod of claim 12, wherein the step of outputting a switching controlsignal comprises: a step in which a driving voltage is outputted to theswitch unit in a predetermined time so that a current can be applied tothe rotor and the rotor can be rotated in a predetermined rotation area;a step in which the switch is turned on by the driving voltage so thatone coil of the stator teeth is excited and the rotor is rotated in thedirection that the coil is excited; and a step in which, when a power ofthe opposite polarity is inputted, the switch is turned on and the otherswitch is turned on, so that the coil at the other side is excited andthe rotor is rotated in the opposite direction.
 15. The method of claim12, wherein, in the step of variably outputting a switch control signal,after the rotational position of the rotor is detected, the switchingcontrol signal for varying a driving voltage of the switch unit isvariably outputted to variably control a rotation angle at which therotor is reciprocally rotated.
 16. The method of claim 12, wherein theswitch is alternately turned on by an AC power to alternately apply thecurrent to the coil of the stator teeth, whereby the rotor isreciprocally rotated.